"The headquarters of those responsible for the terrorist crime in Ahvaz was attacked a few minutes ago east of the Euphrates by several ballistic missiles fired by the aerospace branch of the Revolutionary Guard," the Guard said in a statement. They said the attack was carried out at 2 a.m. local time (2230 UTC) and that the missiles used flew 570 km (354 miles) to their targets.

The statement said many "takfiri terrorists" — a term often used by Iranian officials to describe Sunni Muslim extremists — had reportedly been killed in the attack.

Iran's Fars news agency said the missiles had hit the Syrian border town of Albu Kamal to the west of the Euphrates River, in the eastern province of Deir Ezzor. The town is held by regime forces and allied militiamen who recaptured it from the Sunni extremist group "Islamic State" (IS) in 2007.

The attack comes in the wake of vows by President Hassan Rouhani to provide a "crushing" response to the attack in Ahvaz, which was claimed by two groups: the Ahvaz National Resistance, an ethnic Arab separatist movement within Iran, and by IS. Neither group produced evidence to support their claims.

Iran at first blamed Arab separatists from the attack, but last Monday, Supreme Leader Ayatollah Ali Khamenei suggested that jihadis operating in Iraq and Syria might be behind the shootings.

"This cowardly act was the work of those very individuals who are rescued by the Americans whenever they are in trouble in Iraq and Syria and who are funded by the Saudis and the (United) Arab Emirates," Khamenei was quoted by his official website as saying. Both Saudi Arabia an the UAE say they had nothing to do with the Ahvaz attack.

Twelve Guards were among the 24 people killed in the September 22 attack in Ahvaz, which targeted a military parade held to mark the start of Iran's 1980-1988 war with Iraq. The attack was carried out by five gunmen, who fired on a viewing stand while military officials were watching the parade.